The virology reference laboratory will continue studies on the detection and characterization of human retroviruses. These studies will be geared to ultimately augment the aims of clinical trials being conducted under the auspices of the ACTG. The major thrust will be assessing the utility of PCR to quantitate HIV-1 DNA and RNA. Other efforts will be directed towards analyzing antiretroviral resistance. Further work will be directed at increasing the sensitivity of HIV-1 culture systems and for examining the mechanisms of indeterminate western blot reactivities in HIV-1 infected individuals. Finally the clinical impact of co-infection with HTLV-I and/or II will be examined HIV-1 infected patients.